1. Filed of the Invention
The present invention relates to a method for attaching a fuel injection device to an engine and a fuel injection device.
2. Description of Earlier Technology
Prior to this invention, the inventors of this invention manufactured a fuel injection device adapted to be attached to an engine as shown in FIG. 8. This fuel injection device 123 has the following construction.
This fuel injection device 123 is provided with a pump case 101, a fuel injection pump 102 fixedly secured to the pump case 101, a fuel injection cam shaft 103 bridged within the pump case 101, a connecting portion 105 arranged in an end wall 104 of the pump case 101, and an input end portion 106 of the fuel injection cam shaft 103 projecting from the connecting portion 105.
The pump case 101 is connected at its connecting portion 105 to an engine timing gear case 108. A fuel injection cam gear 107 is fixedly secured to an input end portion 106 of the fuel injection cam shaft 103 in a predetermined position. The pump case 101 connected to the timing gear case 108 is turned about the fuel injection cam shaft 103. When the pump case 101 has stopped its revolution, it is fixedly secured to the timing gear case 108.
The inventors of this invention attached the above-mentioned device 123 to the engine as follows.
The pump case 101 is attached at its connecting portion 105 to the engine timing gear case 108. The fuel injection cam gear 107 is fixedly secured to the input end portion 106 of the fuel injection cam shaft 103 in a predetermined position. The fuel injection cam gear 107 is engaged with an interlocking gear 116 of a crankshaft gear 115 in a predetermined position. Gears of a timing gear train 143 extending from the crankshaft gear 115 to the fuel injection cam gear 107 are mutually engaged with each other by coinciding marks 114 provided in the respective gears.
Differently from this invention, the above-mentioned device 123 is not provided with a means for temporarily stopping revolution of the fuel injection cam shaft 103. Therefore, when attaching this device 123 to the engine, it is necessary to set a fuel injection start timing after the connecting of the pump case 101 to the engine timing gear case 108.
The setting of the fuel injection start timing is carried out as follows.
First, the pump case 101 is temporarily attached to the timing gear case 108 in an arbitrary position. Then, while the crankshaft 117 is turned slowly by hand, a fuel oil level at a fuel delivery port (not illustrated) of the fuel injection pump 102 is observed visually. The time when the fuel oil surface starts to swell is defined as a fuel injection start timing, and at this time, the turning of the crankshaft 117 is stopped. Next, a crank angle is read with reference to a graduation 144 of a flywheel 136 shown by a pointer 146 of a flywheel cover 145 to measure the fuel injection start timing. Then, in order to bring the measured injection start timing to a target value, the temporary attachment of the pump case 101 is released to turn the pump case 101. The position of the fuel injection pump 102 with respect to the fuel injection cam shaft 103 is corrected by this turning and the pump case 101 is then temporarily held. After that, the measuring of the fuel injection start timing and the correcting of the position of the fuel injection pump 102 are repeated until the fuel injection start timing reaches the target value.
There are, however, the following problems accompanied with the above-mentioned earlier technology.
In the above-mentioned earlier technology, the fuel injection start timing is measured based on the visual observation of the starting of the fuel oil surface swelling at the fuel delivery port of the fuel injection pump 102. However, this observation method lacks correctness and is low in measurement accuracy of the injection start timing. Lash or play in the timing gear train 143, caused by gaps between mating or meshed gear teeth, results in lower measurement accuracy of the injection start timing. Since the measurement accuracy of the injection start timing is low, the injection start timing can't be set accurately.
In the above-mentioned earlier technology, the injection start timing is set after the pump case 101 has been connected to the engine timing gear case 108. Since the measurement of the injection start timing and the correction of the position of the fuel injection pump 102 are repeated during that setting, the setting time is relatively long. After the position of the fuel injection pump 102 has been established by that setting, a fuel injection pipe is connected to the fuel injection pump 102. Since the setting of the injection start timing must be accomplished between the connecting of the pump case 101 and the connecting of the fuel injection pipe, the engine assembly must be interrupted for a comparatively long time and the engine assembly becomes stagnated.